1
CA5420A
0.5MHz, Low Supply Voltage, Low Input
Current BiMOS Operational Amplifiers
The CA5420A is an integrated circuit operational amplifier
that combines PMOS transistors and bipolar transistors on a
single monolithic chip. It is designed and guaranteed to
operate in microprocessor logic systems that use V+ = 5V,
V- = GND, since it can operate down to
1V supplies. It will
also be suitable for 3.3V logic systems.
The CA5420A BiMOS operational amplifier features gate-
protected PMOS transistors in the input circuit to provide
very high input impedance, very low input currents (less than
1pA). The internal bootstrapping network features a unique
guardbanding technique for reducing the doubling of leakage
current for every 10
o
C increase in temperature. The
CA5420A operates at total supply voltages from 2V to 20V
either single or dual supply. This operational amplifier is
internally phase compensated to achieve stable operation in
the unity gain follower configuration. Additionally, it has
access terminals for a supplementary external capacitor if
additional frequency roll-off is desired. Terminals are also
provided for use in applications requiring input offset voltage
nulling. The use of PMOS in the input stage results in
common-mode input voltage capability down to 0.45V below
the negative supply terminal, an important attribute for single
supply application. The output stage uses a feedback OTA
type amplifier that can swing essentially from rail-to-rail. The
output driving current of 1.0mA (Min) is provided by using
nonlinear current mirrors.
This device has guaranteed specifications for 5V operation
over the full military temperature range of -55
o
C to 125
o
C.
The CA5420A has the same 8 lead pinout used for the
industry standard 741.
Functional Diagram
Features
CA5420A at 5V Supply Voltage with Full Military
Temperature Range Guaranteed Specifications
CA5420A Guaranteed to Operate from
1V to
10V
Supplies
2V Supply at 300
A Supply Current
1pA (Typ) Input Current (Essentially Constant to 85
o
C)
Rail-to-Rail Output Swing (Drive
2mA Into 1k
Load)
Pin Compatible with 741 Op Amp
Applications
pH Probe Amplifiers
Picoammeters
Electrometer (High Z) Instruments
Portable Equipment
Inaccessible Field Equipment
Battery Dependent Equipment (Medical and Military)
5V Logic Systems
Microprocessor Interface
Pinout
CA5420A
(SOIC)
TOP VIEW
NOTE: Pin is connected to Case.
MOS
BIPOLAR
X1
X1
MOS
BIPOLAR
OTA BUFFER
(X2)
HIGH GAIN
(50K)
BUFFER AMPS;
BOOTSTRAPPED
INPUT PROTECTION
NETWORK
-
+
Ordering Information
PART NUMBER
(BRAND)
TEMP.
RANGE (
o
C)
PACKAGE
PKG.
NO.
CA5420AM
(5420A)
-55 to 125
8 Ld SOIC
M8.15
1
2
3
4
8
7
6
5
+
V+
OFFSET
INV.
INPUT
V-
NON-INV.
INPUT
STROBE
OUTPUT
OFFSET
NULL
NULL
-
Data Sheet
September 1998
File Number
1925.4
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143
|
Copyright
Intersil Corporation 1999
2
Absolute Maximum Ratings
Thermal Information
Supply Voltage (Between V+ and V- Terminals) . . . . . . . . . . . . 22V
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . (V+ + 8V) to (V- -0.5V)
Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1mA
Output Short Circuit Duration (Note 1). . . . . . . . . . . . . . . . Indefinite
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . -55
o
C to 125
o
C
Thermal Resistance (Typical, Note 2)
JA
(
o
C/W)
JC
(
o
C/W)
SOIC Package . . . . . . . . . . . . . . . . . . .
157
N/A
Maximum Junction Temperature (Plastic Package) . . . . . . . 150
o
C
Maximum Storage Temperature Range (All Types) . . . -65
o
C to 150
o
C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300
o
C
(SOIC - Lead Tips Only)
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTES:
1. Short circuit may be applied to ground or to either supply.
2.
JA
is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
Typical Values Intended Only for Design Guidance. V+ = +5V; V- = GND, T
A
= 25
o
C
PARAMETER
SYMBOL
TEST CONDITIONS
CA5420A
UNITS
Input Resistance
R
I
150
T
Input Capacitance
C
I
4.9
pF
Output Resistance
R
O
300
Equivalent Input
Noise Voltage
e
N
f = 1kHz
R
S
= 100
62
nV/
Hz
f = 10kHz
38
nV/
Hz
Short-Circuit Current To
Opposite Supply
Source
I
OM
+
2.6
mA
Sink
I
OM
-
2.4
mA
Gain Bandwidth Product
f
T
0.5
MHz
Slew Rate
SR
0.5
V/
s
Transient Response
Rise Time
t
r
R
L
= 2k
, C
L
= 100pF
0.7
s
Overshoot
OS
15
%
Current from Terminal 8 To V-
I
8
+
20
A
Current from Terminal 8 To V+
I
8
-
2
mA
Settling Time
0.01%
A
V
= 1
2V
P-P
Input
8
s
0.10%
A
V
= 1
2V
P-P
Input
4.5
s
Electrical Specifications
T
A
= 25
o
C, V+ = 5V, V- = 0, Unless Otherwise Specified
PARAMETER
SYMBOL
TEST
CONDITIONS
CA5420A
UNITS
MIN
TYP
MAX
Input Offset Voltage
V
IO
V
O
= 2.5V
-
1
5
mV
Input Offset Current
I
IO
V
O
= 2.5V
-
0.02
0.5
pA
Input Current
I
I
V
O
= 2.5V
-
0.02
1
pA
Common Mode Rejection Ratio
CMRR
V
CM
= 0 to 3.7V, V
O
= 2.5V
75
83
-
dB
Common Mode Input Voltage Range
V
lCR
+
V
O
= 2.5V
3.7
4
-
V
V
lCR
-
-
-0.3
0
V
Power Supply Rejection Ratio
PSRR
V+ = 1V;
V- = 1V
75
83
-
dB
Large Signal Voltage Gain
A
OL
V
O
= 0.5 to 4V
R
L
=
85
87
-
dB
V
O
= 0.5 to 4V
R
L
= 10k
85
87
-
dB
V
O
= 0.7 to 3V
R
L
= 2k
80
85
-
dB
CA5420A
3
Source Current
I
SOURCE
V
O
= 0V
1.2
2.7
-
mA
Sink Current
I
SINK
V
O
= 5V
1.2
2.1
-
mA
Output Voltage
V
OM
+
R
L
=
4.9
4.94
-
V
V
OM
-
-
0.13
0.15
V
V
OM
+
R
L
= 10k
4.7
4.9
-
V
V
OM
-
-
0.12
0.15
V
V
OM
+
R
L
= 2k
3.5
4.6
-
V
V
OM
-
-
0.1
0.15
V
Supply Current
I
SUPPLY
V
O
= 0V
-
400
500
A
V
O
= 2.5V
-
430
550
A
Electrical Specifications
T
A
= 25
o
C, V+ = 5V, V- = 0, Unless Otherwise Specified (Continued)
PARAMETER
SYMBOL
TEST
CONDITIONS
CA5420A
UNITS
MIN
TYP
MAX
Electrical Specifications
T
A
= -55
o
C to 125
o
C, V+ = 5V, V- = 0, Unless Otherwise Specified
PARAMETER
SYMBOL
TEST
CONDITIONS
CA5420A
UNITS
MIN
TYP
MAX
Input Offset Voltage
V
IO
V
O
= 2.5V
-
2
10
mV
Input Offset Current
I
IO
V
O
= 2.5V
-
1.5
3
nA
Up to T
A
= 85
o
C
-
2
10
pA
Input Current
|
I
I
|
V
O
= 2.5V
-
2
5
nA
Up to T
A
= 85
o
C
-
10
15
pA
Common Mode Rejection Ratio
CMRR
V
CM
= 0 to 3.7V,
V
O
= 2.5V
70
80
-
dB
Common Mode Input Voltage Range
V
lCR
+
V
O
= 2.5V
3.7
4
-
V
V
lCR
-
-
-0.3
0
V
Power Supply Rejection Ratio
PSRR
V+ = 1V;
V- = 1V
70
83
-
dB
Large Signal Voltage Gain
A
OL
V
O
= 0.5 to 4V
R
L
=
85
87
-
dB
V
O
= 0.7 to 4V
R
L
= 10k
80
87
-
dB
V
O
= 0.7 to 2.5V
R
L
= 2k
75
80
-
dB
Source Current
I
SOURCE
V
O
= 0V
1
2.7
-
mA
Sink Current
I
SINK
V
O
= 5V
1
2.1
-
mA
Output Voltage
V
OM
+
R
L
=
4.8
4.9
-
V
V
OM
-
-
0.16
0.2
V
V
OM
+
R
L
= 10k
4.7
4.9
-
V
V
OM
-
-
0.15
0.2
V
V
OM
+
R
L
= 2k
3
4
-
V
V
OM
-
-
0.14
0.2
V
Supply Current
I
SUPPLY
V
O
= 0V
-
430
550
A
V
O
= 2.5V
-
480
600
A
CA5420A
4
Electrical Specifications
For Equipment Design at V
SUPPLY
=
1V, T
A
= 25
o
C, Unless Otherwise Specified
PARAMETER
SYMBOL
TEST
CONDITIONS
CA5420A
UNITS
MIN
TYP
MAX
Input Offset Voltage
V
IO
-
2
5
mV
Input Offset Current
|
I
IO
|
-
0.01
4 (Note 3)
pA
Input Current
|
I
I
|
-
0.02
5 (Note 3)
pA
Large Signal Voltage Gain
A
OL
R
L
= 10k
20
100
-
kV/V
86
100
-
dB
Common Mode Rejection Ratio
CMRR
-
560
1000
V/V
60
65
-
dB
Common Mode Input Voltage Range
V
lCR
+
0.2
0.5
-
V
V
lCR
-
-1
-1.3
-
V
Power Supply Rejection Ratio
PSRR
-
32
320
V/V
70
90
-
dB
Maximum Output Voltage
V
OM
+
R
L
=
0.9
0.95
-
V
V
OM
-
-0.85
-0.91
-
V
Supply Current
I
SUPPLY
-
350
650
A
Device Dissipation
P
D
-
0.7
1.1
mW
Input Offset Voltage Temp. Drift
V
IO
/
T
-
4
-
V/
o
C
Electrical Specifications
For Equipment Design at V
SUPPLY
=
10V
,
T
A
= 25
o
C, Unless Otherwise Specified
PARAMETER
SYMBOL
TEST
CONDITIONS
CA5420A
UNITS
MIN
TYP
MAX
Input Offset Voltage
V
IO
-
2
5
mV
Input Offset Current
|
I
IO
|
-
0.03
4 (Note 3)
pA
Input Current
|
I
I
|
-
0.05
5 (Note 3)
pA
Large Signal Voltage Gain
A
OL
R
L
= 10k
20
100
-
kV/V
86
100
-
dB
Common Mode Rejection Ratio
CMRR
-
100
320
V/V
70
80
-
dB
Common Mode Input Voltage Range
V
lCR
+
9
9.3
-
V
V
lCR
-
-10
-10.3
-
V
Power Supply Rejection Ratio
PSRR
-
32
320
V/V
70
90
-
dB
Maximum Output Voltage
V
OM
+
R
L
=
9.7
9.9
-
V
V
OM
-
-9.7
-9.85
-
V
Supply Current
I
SUPPLY
-
450
1000
A
Device Dissipation
P
D
-
9
14
mW
Input Offset Voltage
Temperature Drift
V
IO
/
T
-
4
-
V/
o
C
NOTE:
3. The maximum limit represents the levels obtainable on high-speed automatic test equipment. Typical values are obtained under laboratory con-
ditions.
CA5420A
5
Typical Applications
Picoammeter Circuit
The exceptionally low input current (typically 0.2pA) makes
the CA5420A highly suited for use in a picoammeter circuit.
With only a single 10G
resistor, this circuit covers the range
from
1.5pA. Higher current ranges are possible with suitable
switching techniques and current scaling resistors. Input
transient protection is provided by the 1M
resistor in series
with the input. Higher current ranges require that this resistor
be reduced. The 10M
resistor connected to pin 2 of the
CA5420A decouples the potentially high input capacitance
often associated with lower current circuits and reduces the
tendency for the circuit to oscillate under these conditions.
High Input Resistance Voltmeter
Advantage is taken of the high input impedance of the
CA5420A in a high input resistance DC voltmeter. Only two
1.5V "AA" type penlite batteries power this exceedingly high-
input resistance (>1,000,000M
) DC voltmeter. Full-scale
deflection is
500mV,
150mV, and
15mV. Higher voltage
ranges are easily added with external input voltage attenuator
networks.
The meter is placed in series with the gain network, thus
eliminating the meter temperature coefficient error term.
Supply current in the standby position with the meter
undeflected is 300
A. At full-scale deflection this current
rises to 800
A. Carbon-zinc battery life should be in excess
of 1,000 hours.
3
CA5420A
4
500-0-500
7
+1.5V
5
1
2
-1.5V
10pF
10G
10M
1M
BATTERY
RETURNS
10k
6
M
A
50pA
15pA
5pA
1.5pA
11k
1.5k
1.5k
1k
430
150
68
1%
-
+
1%
1%
1%
FIGURE 1. PICOAMMETER CIRCUIT
2
CA5420A
4
500-0-500
7
+1.5V
5
1
3
-1.5V
10M
22M
BATTERY
RETURNS
10k
6
M
A
500mV
150mV
50mV
15mV
1.1k
1.5k
1.5k
1k
430
150
68
1%
-
+
100pF
1%
1%
1%
FIGURE 2. HIGH INPUT RESISTANCE VOLTMETER
Typical Performance Curves
FIGURE 3. OUTPUT VOLTAGE SWING AND COMMON MODE
INPUT VOLTAGE RANGE vs SUPPLY VOLTAGE
FIGURE 4. OUTPUT VOLTAGE vs LOAD SOURCING CURRENT
R
L
= 100k
10
SUPPLY VOLTAGE (V)
15
T
A
= 25
o
C
-1.0
INPUT & OUTPUT V
O
L
T
A
GE EXCURSIONS FR
OM THE
5
1
0
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0
POSITIVE AND NEGA
TIVE SUPPL
Y V
O
L
T
A
GE (V)
V
O
+
V
ICR
-
V
ICR
+
V
O
-
V+ = 2V
V+ = 5V
V+ = 10V
V+ = 20V
10
1
0.1
0.001
LOAD (SOURCING) CURRENT (mA)
V- = 0V
T
A
= 25
o
C
1000
100
10
OUTPUT ST
A
GE TRANSIST
OR SA
TURA
TION
V
O
L
T
A
G
E,
Q19 (mV)
CA5420A
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